The overall aim of this R34 application is to develop a manual-based cognitive behavioral therapy (CBT) intervention to treat bulimia nervosa (BN) in adolescents identified in primary care. Eating disorders are among the most common, impairing, and serious mental health problems-particularly among women. BN usually arises in adolescence and affects as many as 3% of young women. Yet despite the significance of this condition, there are no systematic studies of empirically-based interventions for adolescents with BN. We propose to design an intervention based on the adult CBT model, addressing developmental considerations of adolescents, as well as the risk and maintaining factors of adolescent BN. In addition to developing the adolescent-specific CBT protocol, we will evaluate adolescent, family, and medical provider satisfaction with this intervention. We will estimate effect-size and effect-size variability of this intervention's impact on primary (binge and purge cessation and frequency) and secondary outcomes measured post treatment and at a 6-month follow-up. These results will inform a subsequent, full-scale, randomized clinical trial. We will develop the intervention in two distinct phases. The first phase (months 1 to 18) will consist of at least two development cycles of the adolescent BN-CBT program. In each cycle, we will draft a version of the intervention, test it with 8-12 clinical cases, obtain feedback from adolescents and their parents, and then generate a new version of the intervention. We will start with a 12-20 session adaptation of the Fairburn, Marcus, and Wilson (1993) CBT intervention, and modify it to fit an adolescent population. The development and revision process will be led by our core Expert Group of clinicians and researchers meeting weekly. We will be guided by the Expert Group's prior experiences developing and evaluating CBT for adult BN, and CBT for adolescent depression; and qualitative feedback from youth, parent, and provider stakeholders. In the second phase (months 19 to 32), we will conduct a larger pilot for the purpose of estimating effect size, using the stable, final version of the intervention. The pilot will enroll 50 adolescents and their families who are identified through their pediatric providers in the HMO. Half of the participants will be randomized to receive the intervention and half to treatment as usual. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]